A single one to do this is:
Code:
(\d{0,1}[,]?\d{0,3}[,]?\d{1,3} [Ww]ords)
It isn't perfect because it would pickup something like "1,,1 Words". But, I suspect that won't appear.
And semantically, "[Ww]" is a bit better than "(W|w)". The former is "One of this list of things" and the later is "W or w and put them into a group for the replacement". It is a little pedantic and doesn't make a difference in your situation. But, if you need to extend this because you found another case, or, needed to replace the text, the latter might not work as well.